The assumption of a constant coupling to the leads should be released for complexes with deep electronic levels, because the wavefunctions of the Fermi-gas electrons in the lead
decays at a significantly different rate as a function of the energy at which they execute the transition, thus affecting the tunneling overlap with the electrodes.
Accordingly, we modulate the coupling \(\Gamma \)  with the transmission probability through the potential barrier separating the lead from the channel.
Assuming for simplicity a rectangular potential barrier of height \(V_B\)  and width \(a\) , the transmission of an electron at energy \(E<V_B\)  is given by [1]}:
\(\vartheta =\left[1+\frac{V_B^2\sinh ^2(ka)}{4E(V_B-E)}\right]^{-1}\) 
